Internal pipe supporting mandrel

ABSTRACT

An improved pipe bending system including a pipe bending machine and an internal pipe supporting mandrel. The pipe bending machine comprises a main frame having connected thereto directly or indirectly a bending die, a stiffback, and a stiffback clamp, a pin-up shoe and a pin-up clamp, an internal stiffback support, and an internal pin-up support. The internal pipe supporting mandrel includes an upper assembly having a plurality of elongated inflatable bags attached thereto, a lower assembly, and means connecting the upper and lower assembly for moving them apart and into engagement with the interior of the pipe. This abstract is neither intended to define the invention of the application which, of course, is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.

United States Patent [191 Calvin et a1.

[451 Dec. 3, 1974 INTERNAL PIPE SUPPORTING MANDREL Campbell, Jr., both of Tulsa, Okla.

[73] Assignee: CRC-Crose International, Inc.,

Houston, Tex.

22 Filed: Jan. 31, 1974 21 Appl. No.: 438,343

Related US. Application Data [62] Division of Ser. No. 260,275, June '6, 1972,

Pat. No. 3,834,210.

3,747,394 7/1973 Cunningham 72/466 Primary Exa miner-Lowell A. Larson Attorney, Agent, or FirmJoe E. Edwards; Jack R. Springgate; Julian Clark Martin [57] ABSTRACT An improved pipe bending system including a pipe bending machine and an internal pipe supporting mandrel. The pipe bending machine comprises a main frame having connected thereto directly or indirectly a bending die, a stiffback, and a stiffback clamp, a pinup shoe and a pin-up clamp, an internal stiffback support, and an internal pin-up support. The internal pipe supporting mandrel includes an upper assembly having a plurality of elongated inflatable bags attached thereto, a lower assembly, and means connecting the upper and lower assembly for moving them apart and into engagement with the interior of the pipe. This abstract is neither intended to define the invention of the application which, of course, is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.

15 Claims, 23 Drawing Figures PATENTEL DEB 31974 sum. 01 or n PATENTE DEC 3|974 sum 02 ur w 7 3851.519 sum as er 11 PATENIL 3E8 31974 PAIENTELBEC 31914 3851519 sum 07 or 11 PATENTEL DEC 3 974 SHEET 7 10 HF 11 PATENILEEE 318M 3.851.519

sum -11 ar 11 INTERNAL PIPE SUPPORTING MANDREL This is a division of application Ser. No. 260,275, filed June 6,1972 now Pat. No. 3,834,210.

BACKGROUND OF THE INVENTION This invention relates to the cold bending'of metallic pipe such as constitutes the end-to-end joint sections in a crosscountry pipeline. More particularly, this invention relates to a bending machine and internal support -nal support mandrels functions excellently to bend pipe. This invention, however, provides an improved pipe bending system, including an improved pipe bending machine and an improved internal support mandrel, having advantages over the prior art.

It is an object of this invention to provide an improved self-contained pipe bending system of relatively small bulk, both transversely and vertically, and of minimum weight for ease of transit.

It is an object of this invention to provide a selfcontained pipe bending system which may be utilized to bend pipe in rough terrain.

It is an object of this invention to provide a pipe bending system which imparts an improved bend to thin wall, high strength alloy, large diameter pipe, including more accuracy in the degrees of bend, less deformity in the circular shape of the pipe, and fewer wrinkles in the skin of the pipe.

It is an object of this invention to provide a pipe bending system which imparts to the pipe a bend of v shorter radius than that imparted by existing systems.

It is an object of this invention to provide a pipe bending system in which the bend may be imparted to the pipe closer to the end of the pipe than with previously existing systems and thus allowsmore bend to be imparted to a segment of pipe.

It is an object of this invention to provide a pipe bending system having an improved internal support mandrel which is capable of expanding more rapidly and providing greater support than previously existing mandrels.

It is a further object of this invention to provide a pipe bending system having an improved internal support mandrel capable of accurately directing its support forces whereby the shape of the pipe may be affirmatively controlled.

The invention itself, both as to organization and method of operation, as well as additional objects and advantages thereof, will become readily apparent from the following description when read in connection with the accompanying drawings, in which like numerals represent like parts:

FIG. 1 is a side elevation view of the preferred pipe of this invention; the internal support mandrel is not shown.

FIG. 2 is a plan view of the preferred pipe bending machine illustrated in FIG. 1.

FIG. 3 is a schematic sectional view of the preferred pipe bending machine taken at lines 3-3 in FIG. 2 with a schematic illustration of the preferred internal support mandrel added thereto.

FIG. 4 is a sectional view of the outer stiffback support assemblies and the stiffback of the preferred pipe bending machine taken at lines 44 in FIG. 1.

FIG. 5 is a sectional view of the stiffback clamp of the preferred pipe bending machine taken at lines 55 in FIG. 1.

FIG. 6 is a plan view of the stiffback clamp illustrated in FIG. 5.

FIG. 7 is a sectional view of the inboard stiffback cylinder and piston assemblies, the die support, the bending die, and the stiffback of the preferred pipe bending machine taken at line 77 in FIG. 1

FIG. 8 is a sectional view of the pin-up clamp, pin-up shoe and wedge of the preferred pipe bending machine taken at lines 8-8 in FIG. 1.

FIGS. 914 are a series of schematic views of the preferred pipe bending system according to this invention illustrating the preferred method of bending pipe according to this invention.

FIG. 15 is a schematic side elevation view of a preferred internal support mandrel according to this invention positioned in its collapsed condition inside a pipe.

FIG. 16 is a detail sectional view of the preferred internal support mandrel taken at lines 16-16 inFIG. 15.

FIG. 17 is a detail sectional view of the preferred internal support mandrel taken at lines 17-17 in FIG. 16.

FIG. 18 is a detail sectional view of the preferred internal support mandrel taken at lines l8-l8 in FIG.

bending machine of the improved pipe bending system I FIG. 19 is a detail sectional view of the preferred internal support mandrel also taken at lines 16-16 in FIG. 15 with the mandrel in its expanded condition and with movement compensators added to certain of the mechanical linkages.

FIG. 20 is a schematic view of certain components of the preferred hydraulic connections between the inflatable bags attached to the upper assembly of the preferred internal support mandrel.

FIG. 21 is a schematic view of certain components of the preferred hydraulic connections between the outboard and inboard stiffback cylinder and piston assemblies of the preferred pipe bending machine.

FIGS. 22 and 23 are schematic illustrations of the prior art bending of pipe and the bending of pipe according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The improved, self-contained, portable pipe bending system according to this invention, which is capable'of accurately bending thin wall, large diameter pipe, includes a pipe bending machine and an internal pipe supporting mandrel. A preferred pipe bending machine 20 according to this invention is illustrated in side elevation in FIG. 1 and in plan in FIG. 2. The pipe bending machine 20 preferably comprises a heavy-duty main frame to which is attached directly or indirectly the other components of this pipe bending system. The improved internal pipe supporting mandrel, not shown in FIGS. 1 and 2, rests within a component attached to the main frame as will hereinafter be explained.

The main frame of the pipe bending machine preferably comprises two heavy-duty, metallic, planar side frames 21 and 22 secured to each other by a plurality ofstout crossmembers or transverse beams 23, 24 and 25. Each of the side frames 21 and 22 preferably is of unitary construction with cavities or holes cut therein at low-stress points to reduce the weight and to facilitate the movement of certain cylinder and piston assemblies as will hereinafter be explained. The ends of each of the transverse beams 23, 24 and 25 not only are welded to the side frames, but in order to strengthen the pipe bending machine, also extend through holes cut in the side frames 21 and 22. The side frames and the transverse beams produce a main frame which, when viewed from the end, presents an open, rectangular framework into which the pipe to be bent may be inserted To facilitate describing this invention, the end of the preferred pipe bending machine into and out of which the pipe is moved (the'rear of the machine or the end on the right of the machine as viewed in FIG. 1) shall be referred to as the pin-up end; the other end of the machine shall be referred to as the stiffback end.

Secured to each of the side frames 21 and 22 at selected positions relatively near the pin-up end of the machine is a set of Athey tracks or an endless track assembly 26 and 27, respectively, such as is well known to those skilled in the art. The bottoms of side frames 21 and 22 preferably are cut so they are off the ground at the pin-up end of the machine and rest on the ground at the stiffback end of the machine. Thus, when the pipe bending machine is 'in position to bend pipe, the four points in contact with the earth will be the two sets of Athey tracks 26 and 27 and the bottoms of the side frames 21 and 22 at the stiffback end of the machine.

Referring now to FIGS. 1, 2, 3 and 7, there is mounted within the top of the main frame a die support 28. Die support 28 preferably is a cast iron shell constructed to present a downwardly facing supporting surface to receive the die against which the pipe is to be bent. Die support 28 is secured within the main frame by journaling the four transverse beams 24 through reinforcing receiving rings 29 mounted in holes cut in the sides of the die support. The bending die 30 comprises an elongated metallic plate which fits into the downwardly facing cavity of die support 28. Preferably there is a pin 31 protruding upwardly from the metal plate of the die 30 into a receiving hole in die support 28 which functions to lock the die into a fixed relationship with the die support. The die 30 is removably secured within die support 28 by bolting together lugs extending from both of the members. The metal plate of die 30 presents a downwardly facing surface that is concave in transverse section and convex in longitudinal section on the arcuate path to which the pipe 'will conform during bending. The portions of the die surface which engage the pipe during bending preferably have attached thereto replaceable resilient linings such as are disclosed in the prior copending application of Edward A. Clavin and Lionel H. Wheeler, Ser. No. 4

236,879, filed Mar. 22, 1972.

verse section throughout its length. As particularly il- Iustrated in FIGS. 2 and 3, stiffback 32 extends from a plane near the stiffback end of the machine to a plane adjacent the end of the bending die nearest the pinup end of the machine. The stiffback 32 is comprised ofa metallic framework supporting an elongated, transversely concave heavy-duty metallic plate 33. To further facilitate description of this invention, the end of the stiffback 32 positioned adjacent the stiffback end of the machine shall be referred to as the outboard or outer end of the stiffback; the other end of the stiffback 32 shall be referred to as the inboard or inner end.

Secured within the framework of the stiffback 32 at selected positions adjacent its inner end are two pairs of reinforcing rings 34 for receiving two transverse, inboard stiffback shafts 35. The ends of the two transverse shafts 35 protrude through a cavity 36 cut in each of the side frames 21 and 22 far enough to have inboard stiffback cylinder and piston assemblies secured thereto. There are two inboard stiffback cylinder and piston assemblies on each side of the main frame. Each of these cylinder and piston assemblies 37, 38, 39 and 40 is secured by ordinary means between a protruding end of one of the transverse beams 24 supporting die support 28 and an end of one of the inboard stiffback shafts 35. Preferably each of the beams 24 and shafts 35 extends through a flange 41 attached to the cylinder and piston assembly and is secured thereto with a collar 42 and pin 43. The pair of transverse beams 25 welded to side frames 21 and 22 adjacent the stiffback end of the machine extend through the side framessufficiently to provide support for a pair of outboard cylinder and piston assemblies 44 & 45 and 46 & 47 on each side of the main frame. Each of these pairs of outboard cylinder and piston assemblies 44 & 45 and 46 & 47 is secured by ordinary means between the two transverse beams protruding on its side of the main frame and an outer stiffback support assembly 48 and 49, respectively. As shown particularly in FIGS. 1, 2 and 4, each of the outer stiffback support assemblies 48 and 49 is comprised of two stout, parallel T-bar plates 50 joined together. The cylinder and piston assemblies are secured to the outer stiffback support assemblies by pins 51 extending through the plates. Each of the T-bar plates comprising the support assemblies 48 and 49 includes a leg which extends downwardly between the two cylinder and piston assemblies attached to the particular support assembly. Mounted within the stiffback framework is a reinforcing ring (not shown) through which is journaled a transverse outboard stiffback shaft 52. Outboard stiffback shaft 52 protrudes beyond the stiffback frame on each side thereof a sufficient distance to extend through and be secured to the downwardly extending legs of the two outer stiffback support assemblies 48 and 49. Secured to the top of the stiffback frame on each side thereof adjacent the middle of the outer stiffback support assemblies 48 and 49 are metallic blocks 53 each of which supports a laterally extending pin 54. Each of the pins 54 extends through an elongated traveling slot 55 in the adjacent outer stiffback support assembly and thus functions as a guide pin dur- .58 in which is rotatably mounted a transverse pin 59.

The transverse pin 59 rotatably rests on a pair of rocking elements 60 (shown in FIG. 3 detached from the pin). Each of the rocking elements 60 is attached to an arm 61 which is rotatably secured by a pin 62 to the main frame near the inner end of the stiffback 32. Longitudinally slidable between a supporting plate 63 secured to the transverse beams 23 and the rocking elements 60 is a pair of interconnected wedges 64. The pair of wedges 64 is affirmatively moved longitudinally in both directions by a cylinder and piston assembly 65 pinned to the main frame. Thus, the pin-up shoe 57 is mounted for movement in the vertical arc transcribed by the pin 59 moving about pin 62 responsive to the movement of the wedges 64. Moreover, pin-up shoe 57 is mounted for rotation about pin 59 to conform to the longitudinal slopeof the pipe held therein.

It can now be observed that the preferred pipe bending machine according to this invention bends pipe by securing it between the cooperating bending die 30, stiffback 32 and pin-up shoe 57. A length of pipe inserted in the stiffback 32 and pin-up shoe 57 as illustrated in FIG. 3 is bent about the bending die by moving the outboard end of stiffback 32 upwardly. The

' inboard stiffback shafts conjunctively act as a pivot for the stiffback 32. Pin-up shoe 57 acts as the fulcrum or support means for the rearward end of the pipe to prevent it from moving downward.

Secured to the pin-up shoe is a pin-up clamp 66 which functions to provide full circular support for the pipe contained in the pin-up shoe 57. However, since most of the forces generated by the portion of the pipe in the area of the pin-up shoe during bending are downward against the pin-up shoe 57 and there is little tendency for the pipe to egg out laterally in this area, the pin-up clamp 66 does not have to be constructed of great strength. FIG. 8 illustrates a preferred pin-up clamp 66 comprising two semicircular arcuate plates 67 and 68 hinged to the top edges of the sides of the pin-up shoe. The opposing ends of the two plates 67' and 68 are joined together with a cylinder and piston assembly 69.

It has been found that the mere combination of the bending die 30 and the stiffback 32 is not sufficient to bend properly large diameter, thin-wall pipe. Dueto the enormous forces generated during bending, the pipe tends to bulge or egg out laterally at points along its length which are supported by the stiffback. Accordingly, as illustrated in FIGS. 1, 2, 3, 5 and 6, in the preferred embodiment of this invention, there is secured to stiffback-32 a stiffback clamp 72 which functions conjunctively with stiffback 32 to provide full cir cular support forthe exterior of the pipe 73 longitudinally of the die 30 during bending. Stiffback clamp 72 preferably is comprised of two arcuate metallic plates 75 and 76 securely hinged to the stiffback 32. The space around each of the hinges between the arcuate plates 75 and 76 and the top of the stiffback, preferably is filled with a weld 77 so that pipe cannot wrinke out. Welded or otherwise connected to arcuate plate 75 is an arcuate connecting plate 78. Arcuate connecting plate 78 is slidable over the outside circumference of arcuate plate 76 and is secured to plate 76 through a locking toggle mechanism 79 well known to those skilled in the art. Locking toggle mechanism 79 is hydraulically operated by cylinder and piston assembly 80. FIG. 5 illustrates the stiffback clamp 72 in its open position with dashed lines. Contraction of the hydraulic cylinder and piston assembly 80 causes the stiffback clamp 72 to assume its closed position shown drawn with solid lines. When the pivot point 81 of the locking toggle mechanism has crossed the centerline between the pivots 82 and 83, the stiffback clamp 72 is mechanically locked into closed position.

In the preferred embodiment of this invention, the stiffback 32 does not provide a full semicircle of support. Rather, to facilitate movement of a pipe 73 into, along and out of the stiffback 32, as illustrated in FIG. 5, the sides of the stiffback 32 do not quite reach up to the horizontal centerline 74 of the pipe 73 held therein. The stiffback clamp 72 and, as illustrated in FIGS. 7 and 8, the bending die 30 and the pipe-up clamp 66 provide the remainder of the required circular exterior support for the pipe 73 during bending. v

The stiffback clamp 72 preferably is located as close as possible to the outboard end of the bending die 30. In the preferred embodiment of this invention, the stiffback clamp 72 is illustrated positioned close enough to the bending die 30 to provide the needed support but far enough away to allow the bending die 30 to be removed from within the'die'support 28 and a new bending die 30 substituted therefor.

The construction of the stiffback clamp 72 is, of

course, not limited to that described herein. Numerous forms of rugged, strong clamps may be used to provide the needed exterior support for the pipe. Also, the stiffback 32 itself may be constructed to be more fully circular to provide additional exterior support for the pipe.

Secured to the outboard end of the stiffback assembly 32 is a tongue assembly 86. Tongue assembly 86 provides a means by which the entire bending machine may be grasped by a tractor or the like and towed to preselected positions. Secured to the tongue assembly 86 adjacent the stiffback end of the main frame is a roller support assembly 87. Roller support assembly 87 functions to lift the pipe slightly from the stiffback 32 when the stiffback 32 and the tongue assembly 86 are at their lowest position. This facilitates easy movement of the pipe longitudinally through the main frame. Roller support assembly 87 preferably comprises two T- shaped flanges 88 and 89, each of which is pivotally secured to opposite sides of the tongue assembly 87. Secured between the two Tshaped flanges 88 and 89 is a transverse shaft 90 which supports conically shaped rollers 91 and 92. Each of the T-shaped flanges 88 and 89 has a receiving slot 93 cut therein to receive a pin 94 protruding from the side of tongue assembly 87. Secured to the inside of each of side-frames 21 and 22 is a horizontal plate (not shown). The plate is positioned and the T-shaped flanges are shaped so that when the stiffback assembly 32 and its attendant tongue assembly 87 are in their lowest position, the roller support assembly 87 has contacted the plate and has moved upwardly thereby lifting rollers 91 and 92. When the stiffback assembly 32 and tongue assembly 87 are raised, the T-shaped flanges 88 and 89 move downwardly until the pins 94 strike the upper surfaces of the slots 93. This downward movement is sufficient to lower the pipe contacting surfaces of rollers 91 and 92 below the bottom of the supporting plate 33 of the stiffback. Thus, the pipe is allowed to rest within the stiffback.

Another set of conically shaped rollers 95 and 96 is carried by the main frame intermediate the inner end of the stiffback 32 and the pin-up shoe 57. These rollers 95 and 96 project above the bottom of the supporting plate 33 of the stiffback and the bottom of the concave supporting surface of the pin-up shoe 57 at their lowered positions so the pipe can be easily brought into and rolled through the main frame.

Attached between side frames 21 and 22 above the die support 28 is a metallic plate 98 which supports a power winch 99 and other additional peripheral machinery. A cable leading from the drum of power winch 99 is utilized to pull the pipe through the main frame as will hereinafter be explained.

Mounted to side frame 21 is an internal combustion engine 100 for powering the various components of the pipe bending machine, including a pressure source (not shown) for the various cylinder and piston assemblies. The operation of the pipe bending machine and its various components, as well as the internal support elements to be hereinafter described, are controlled at the operators station 101 through a-group of hand lever actuated valves.

The conduits and valves for supplying hydraulic fluid under pressure to the inboard and outboard stiffback cylinder and piston assemblies, the stiffback clamp, the pin-up clamp, and the pin-up shoe are not shown in FIGS. 1, 2 or 3 and are not described herein in detail.

It is believed that the manner of providing such hydraulic fluid to the various components of the bending machine is within the province of those skilled in the mechanical arts. For guidance, the artisan is referred to the hydraulic systems described in Coody U.S. Pat. No. 2,740,453 and Cummings U.S. Pat. No. 3,335,588. It is believed important, however, to point out particularly the manner of providing hydraulic fluid to the in-- board and outboard stiffback cylinder and piston assemblies in the preferred embodiment of this invention. As illustrated in FIG. 21, hydraulic fluid is supplied through conduit 102 to the stiffback control valve 103. The flow from control valve 103 is directed through a sequence valve 104 which functions to insure that a preselected magnitude of hydraulic pressure is supplied through conduit 105 to the inboard stiffback cylinder and piston assemblies 37, 38, 39 and 40 before sufficient hydraulicpressure. is supplied through conduit 106 to the outboard stiffback cylinder and piston assemblies 44, 45, 46 and 47 to impart bend to the pipe. The sequence valve used may be any of numerous commercially available devices such as a Vickers RC CT 10. A relief valve 107 is attached to the system for rapidly dumping the hydraulic fluid should the need arise. This system of supplying hydraulic fluid to the stiffback cylinder and piston assemblies allows the operator properly to apply bend to the pipe as will hereinafter be explained.

In order to impart a proper cold bend to large diame ter, thin-wall pipe, wherein the bent pipe is circular in transverse section and is not wrinkled or crimped, it is necessary to provide internal support for the pipe during the bending process. The improved pipe bending system according to this invention includes an internal stiffback support 110, an internal pin-up support 111, and an internal pipe support mandrel 112. Referring to FIGS. 1, 2 and 3, the internal stiffback support 110 and pin-up support (not shown) function to prevent the pipe from buckling, wrinkling or crimping inwardly at points spaced from the bending die 30. The mandrel l 12 functions to prevent the pipe from buckling, wrinkling or crimping inwardly adjacent the bending die 30. The internal stiffback support 110 and pin-up support 111 preferably are aligned and utilized with the stiffback clamp 72 and the pin-up clamp 66, respectively. The mandrel 112 is, ofcourse, utilized with the bending die 30.

It has been determined that the internal stiffback support 110 and pin-up support 111 need not be used conjunctively with the stiffback clamp 72 and pin-up clamp 66 with every bend of the pipe. Each is needed only when an end of the pipe is adjacent or in the respective stiffback clamp 72 or pin-up clamp 66. For example, in FIG. 3, neither end of the pipe 73 is adjacent the stiffback clamp 72 or the pin-up clamp 66 and thus neither the internal stiffback support 110 nor the internal pinup clamp 111 is needed. Due to this selective need for the internal stiffback support and the pin-up support, in the preferred embodiment of this improved pipe bending system each is mounted on the pipe bending machine 20 rather than on the mandrel 1'12. Preferably, there is a pair of flanges 113 secured to side frame 21 adjacent the pin-up end of the machine and to the outer stiffback support assembly 48. Rotatably journaled in each pair of the flanges 113 is a vertical beam 114. Securedto each of the beams 114 and extending outwardly therefrom is a horizontal davit 115 carrying a horizontally movable trolley assembly 116 (the pinup trolley assembly is not shown). Depending from each of the trolley assemblies 116 through a universal joint assembly 117 and 118 and a flexible expansible cylinder and piston assembly 119 is the respective internal stiffback support or internal pin-up support. Each of the internal stiffback support 110 and the internal pin-up support 111 is inserted into the end of the pipe manually by swinging the davit into position and adjusting the height and location of the support until it will enter the pipe. Although the internal stiffback support 110 and pin-up support 111 are'preferably mounted on the pipe bending machine, either or both of them alternatively may be attached to the ends of the internal support mandrel 112 so that when the mandrel 112 is properly positioned with respect to the bending die 30 each of the supports 110 and 111 is properly positioned with respect to the stiffback clamp 72 and pin-up clamp 66, respectively.

The preferred construction of the internal stiffback support 110 and pin-up support 111 will be described after the mandrel 112 is described.

The improved internal pipe supporting mandrel 112 interior of the pipe adjacent the pipe bending die during bending. Attached to the two ends of the upper assembly 120 in a manner to be hereinafte'rexplained are end plates 122 and 123. Secured to each of the end plates 122 and 123 is a downwardly extending wheel support assembly including a plurality of supporting arms 124. Rotatably attached to each of the wheel support assemblies are at least two wheels 125 for allowing the mandrel 112 to move along the stiffback 32 and into, along and out of the pipe 73. The construction of the wheel support assemblies and the attachment of the wheels thereto may be similar to that described in Avera, et al, US Pat. No. 3,109,477 provided. of course, that the wheels and wheel support assemblies depend only from the upper assembly 120 of the mandrel. Power means are secured to thewheels and within the wheel support assembly on one end of the mandrel to provide rotational force to the wheels and thereby move the mandrel. This power means may be a diesel engine, a fluid motor as described in Avera, et al, US. Pat. No. 3,109,477, or any other commercially available device well-known to those skilled in the art. In the preferred mandrel according to this invention, the lengths of the supporting arms 124 comprising the wheel support assemblies are chosen such that the wheels [25 are in contact with the curved supporting surface, whether it be the stiffback 32 or the pipe 73, only when the mandrel 112 is collapsed. On the other hand, when the mandrel 112 is expanded as will hereina after be explained, the upper assembly 120 moves upwardly and thereby moves the wheels 125 upwardly out of contact with the supporting surface. Alternatively, the wheels 125 may be attached to pivotal members which can selectively move the wheels radially into and out of contact with the supporting surfaces as taught in Avera, et al, us. Pat. No. 3,109,477.

The preferred construction of the upper and lower assemblies 120 and 121- and the interconnecting mechanical linkages is illustrated in FIGS. 16 through 19. The upper assembly 120 comprises an elongated, transversely plano-convex support apparatus which provides a longitudinally flexible transversely convex foundation for a pluralityof hydraulic packers enveloped in a resilient material. The lower assembly 121 comprises an elongated, transversely plano-convex support apparatus which provides a longitudinally flexible, transversely convex foundation for means for engaging the lower portion of the pipe. Connecting the upper and lower assemblies 120 and 121 is a mechanical assembly which functions to move the upper and lower assemand toward (referred to as contracting or collapsing the mandrel) each other. Unlike many of the prior art mandrels, the improved mandrel according to this invention does not have a perfectly circular transverse shape when collapsed and does not expand radially to maintain a circular shape. Rather, its transverse shape when collapsed is that of two adjacent plane-convex segments, the convex circular surface of each being less than a semicircle. When the mandrel is expanded, the two plane-convex segments are moved away from each other and into engagement with opposite portions of the interior of the pipe, thereby providing a substantially circular support.

The mandrel is utilized with the apexes of the upper and lower assemblies substantially aligned with the plane passing through the apex of the pipe in the direction of the bend being imparted to the pipe. The upper assembly is in contact with the portion of the pipe associated with the bending die the portion of the pipe which is compressed by the bend. The lower assembly 121 is in contact with the portion of the pipe associated with the stiffback the portion of the pipe which is expanded or stretched by the bend. There is no internal support provided by the mandrel for the pipe between the upper and lower assemblies because the pipe in that area does not tend to buckle, wrinkle or crimp inwardly during bending.

The elongated, transversely plano-convex support apparatus of the upper assembly 120 preferably comprises first and second, elongated, planar, rectangularly-shaped spring steel members and 126 laterally spaced apart from each other and extending the length of the upper assembly. Secured by welding or otherwise to the ends of the spring steel members 125 and 126 are the stout, transversely, plane-convex end .plates 122 and 123. Secured to the two spring steel members 125 and 126 between the end plates 122 and 123 are seven identical convex foundation segments. Each of the seven segments preferably comprises a curved sheet 127 of spring steel arcing laterally between the two elongated spring steel members 125 and 126 with one end of the curved sheet 127 welded or otherwise se- .cured to each of the members 125 and 126. The extecurved sheets 127 of-spring steel and functions as a part of the foundation for the hydraulic packers and the enveloping resilient material. Each of the seven curved sheets 127 has a plano-convex rib 128 welded or otherwise attached to the inside thereof and between the two spring steel members 125 and 126. A plurality of circular, steel supporting rods 129 extend through the end plates 122 and 123 and'through each of the seven curved sheets 127 of the upper assemblies. The rods 129 are attached to the end plates by welding or otherwise but slip through holes in the ribs 128 of the seven curved segments so that the foundation segments are free to move longitudinally thereon. A plurality of elongated back-up steel spring strips 130 are laid longitudinally along the exterior of the seven curved sheets 127 between the end plates 122 and 123. These elongated back-up strips 130 are not connected to the curved sheets 127. In securing the curved sheets 127-to the elongated members 125 and 126 between the end plates 122 and 123, a small space 131 preferably is left between adjoining segments. This allows the curved foundation segments to contract toward each other and thus insures longitudinal flexibility of the upper assembly 120. Arranged along the exterior of the elongated back-up strips 130 between the end plates 122 and 123 is a compressible, resilient material, such as polyurethane solid elastomer in the durometer range of 85 to 95. Preferably the resilient material is attached to the upper assembly in the form of seven curved segments 132, each of which is the same length as a corresponding curved sheet 127 and which is a truncated circular sector in transverse section. Each of the segments 132 which will behereinafter described.

Secured to the two end plates (not shown in FIG. 17) and extending along the length of the upper assembly are a plurality of triangular filler springs 133. Each filler spring 133 is adjacent to and overlaps two of the elongated back-up strips 130. Each of filler springs 133 fits between two of the elongated segments 132 of resilient material in triangular spaces cored therein. Also secured to the end plates (not shown in FIG. 17) and extending longitudinally along the length of the upper assembly are a plurality of elongated, circular spring steel tie-bars 134. Each tie-bar 134 is secured between two of the segments 132 of the resilient material in elongated, transverse semicircular grooves cored in the sides thereof.

Extending through a relatively large, longitudinal, circular cavity in each segment 132 of the resilient material is an elongated inflatable bag 135, such as a Lynes hydraulic packer. Each of the packers 135 extends through and slightly beyond the two end plates 122 and 123. The ends of the hydraulic packers 135 preferably are hydraulically interconnected to each other (not shown) and to attendant hydraulic equipment (not shown) carried in the wheel support assemblies in the manner schematically illustrated in FIG. 20, which will be hereinafter described.

Extending from the end plates 122 and 123 along the length ofthe upper assembly are a plurality of relatively flat, spring steel surface integrating strips 136. Each surface integrating strip 136 fits within longitudinal receiving grooves cored in the exterior surface of the seven segments 132 of the resilient material so that the exterior surfaces of the strips 136 are flush with the exteriorsurfaces of the segments 132. As illustrated in FIG. 17, each end plate (only end plate 122 being shown) has an inwardly facing flange 137 along its convex surface. The segment 132 of resilient material adjacent each end plate has a shoulder cored out of its convex exterior surface to receive the flange. Receiving grooves are cut in the convex surface of the end plates to align with the receiving grooves cut in the exterior surfaces of the segments 132', the surface strips 137 extend over the end plates 122 and 123 and arebolted thereto.

, Secured across and connecting the undersides of the two elongated spring steel members 125 and 126 are seven transverse upper jaw members 140. Each of the upper jaw members 140 has horizontal flanges 141 extending outwardly therefrom so the upper jaw member 140 can be bolted to the elongated members 125 and 126 vertically below a supporting rib 128. Each of the upper jaw members 140 includes a plurality of downwardly facing cam surfaces 142 and shoulders 143.

The elongated, transversely plano-convex support apparatus of the lower assembly 121 preferably comprises seven transverse planar lower jaw members 144. Each transverse lower jaw member 144 is constructed to have a downwardly facing convex surface and a plurality of upwardly facing cam surfaces 142 and shoulders 143 corresponding to' the cams and shoulders of the upper jaw members 140. To decrease the weight of the lower jaw members 144, each of them preferably contains a large internal cavity 145 with a planeconvex rib 146 welded therein. Secured to the downwardly facing convex surfaces of the seven lower jaw members 144 and extending longitudinally along the length of the lower assembly are a plurality of pairs of spring steel strips 147. Attached to the exterior surfaces of the spring steel strips 147 throughout the lower assembly are a plurality of pipe engaging resiliently compressible blocks 148, each of which preferably is constructed of the previously described polyurethane. The blocks 148 are bolted (not shown) to the strips 147 and, as illustrated in FIG. 16, when a block is aligned with a lower jaw member 144, both the block 148 and the strips 147 are bolted to the lower jaw member.

Each of the seven lower jaw members 144 is positioned vertically below an upper jaw member 140. P0- sitioned between each pair of upper and lower jaw members 140 and 144 are a pair of vertically disposed toggle bars 149. Each toggle bar 149 has a plurality of protruding bosses 150 which communicate with the cam surfaces 142 and shoulders 143 of the upper and lower jaw members 140 and 144. Each of the toggle bars 149 is linked for transverse movement to both the upper and lower jaw members through a plurality of mechanical linkages 151. The mechanical linkages 151 are designed only to guide the transverse movement of the toggle bars 149. They are not designed to transfer vertical forces. Vertical forces are transferred to the upper and lower assemblies and 121 by the bosses 150 of the toggle bars moving transversely against the cam surfaces 142. I

FIG. 17 illustrates the mandrel in its collapsed position. Both of the toggle bars 149 are positioned in their most inward transverse position. The bosses 150 are resting in the cavities between the shoulders 143 of the upper and lower jaw members and 144. As force is applied to the toggle bars 149 to move them transversely outwardly away from each other, the bosses move into contact with the cam surfaces 142 and, as illustrated in FIG. 19, thereby force apart the upper and lower jaw members 140 and 144. When the toggle bars 149 have moved to their extreme outward position, the mandrel is expanded. When the mandrel is expanded, the bosses 150 on the toggle bars 149 are in alignment and engagement with the shoulders 143 on i the upperand lower jaw members 140 and 144 and thus provide direct mechanical support locking the mandrel in its expanded condition. y

The preferred apparatus for moving each of the toggle bars 142 in a pair thereof alternatively away from and toward each other is a plurality of cylinder and piston assemblies 152. Preferably six toggle bar cylinder and piston assemblies 152 are utilized in parallel, each of which is positioned in the space existing between adjacent pairs of the toggle bars. As illustrated schematically in FIG. 15 and in detail in FIG. 18, the toggle bar cylinder and piston assemblies 152 are connected in pairs to opposing drive flanges 153. Each of the drive flanges 153 extends through and is secured to one toggle bar 149. Each drive flange 153 has welded thereto an elongated hollow sleeve 154 which also is secured to and passes through the same toggle bar as the drive flange. Extending through the three aligned sleeves 154 and the seven aligned toggle bars 149 on each side of the mandrel is a continuous, circular drive bar 155 having an outside diameter less than the inside diameter of the sleeves 154. Thus, expansion and contraction of the six toggle bar cylinder and piston assemblies 152 causes the pairs of drive bars 153, sleeves 154 and toggle bars 149 attached thereto to move away from or toward each other. Movement of the pairs of sleeves produces movement of the two drive bars 155, which in turn produces transverse movement of the remaining toggle bars 149. Since the sleeves 154 are larger than the drive bars 155, the drive bars may freely bend with the longitudinal flexing of the mandrel.

FIG. 19 illustrates an optional apparatus which may be attached to the linkage mechanism to insure that each toggle bar 49 in a pair moves transversely outwardly an equal distance. Sequred to each of the innermost mechanical linkages (not shown) is a square drive pin 156. A sprocket wheel 157 having teeth around its circumference is secured to each drive pin. Chains 158 are linked around opposing sprocket wheels in opposite directions whereby outward movement of one toggle bar causes rotation of the sprocket wheels attached to its pivoted linkages and equal but opposite rotation of the sprocket wheels attached to the pivoted linkages of the opposing toggle bar thereby producing an equal outward movement of the opposing toggle bar.

In the preferred embodiment of the internal support mandrel according to this invention, there are eleven elongated hydraulic packers 135 enveloped in the polyurethane around the convex supporting surface of the in FIG. 20. The five packers 135a positioned from the apex of the upper assembly to approximately to either side thereof are hydraulically connected in parallel. The remaining six packers b, the three on either side of the'five center packers, are also hydraulically connected in parallel. Hydraulic fluid from tank 159 is pressurized by pump 160 and supplied through conduit 161 to valves 162 and 163 controlling the input to the five center packers 135a and the six outlying packers 135b, respectively. Valves 164 and 165 control the flow of the hydraulic fluid'through conduit 166 back to the tank. By selectively opening and closing the valves 162, 163, 164 and 165, varying pressures can be maintained on the two sets of packers. For example, valves 164 and 165 canbe closed and the input valves 162 and 163 opened. When the pressure in all of the packers has risen to a preselected magnitude such as 600 psi, valve 163 may be closed. The pressure will continue to build in the five center packers to a selected higher magnitude, such as 800 psi, until valve 162 is closed. By so selectively maintaining the pressure of the center packers higher than the pressure of the outlying packers, the pipe to be bent can be preshaped to egg out slightly vertically. Then when the bending forces are applied to the pipe and the pipe tends to egg" out slightly laterally, a more circular shape will be produced in the bent pipe than is accomplished by prior bending systems.

The construction of the internal stiffback support 110 and the internal pin-up support 111 preferably is similar to the construction of the internal support mandrel 112. Each of the internal supports 110 and 111 comprises a single segment of the internal support mandrel 112. The first and second elongated spring steel members 125 and 126 described with respect to FIG. 17 are shortened to coincide with the length of a single curved sheet 127 of spring steel and two adjacent end plates. The lengths of the elongated hydraulic packers are of course also decreased. There is preferably only one set of toggle bars, which are pivotally attached to an upper jaw member secured to the upper assembly vertically beneath the supporting rib 128. There is preferably only one lower jaw member 144 utilized. Secured to the sole lower jaw member around its convex lower surface are shortened strips of spring steel and pipe engaging blocks. Preferably two toggle bar cylinder and piston assemblies are utilized, one on each side of the pair of toggle bars. The movement of the cylinder and piston assemblies 152 is transmitted to the toggle bars through drive flanges 153 attached to the toggle bar. The hydraulic fluid preferably is conducted to the cylinder and piston assemblies through flexible hoses (not shown) extending from the supports 110 and 111 to tanks and pumps (not shown) attached to the main frame of the pipe bending machine.

Additional advantages of this improved pipe bending system will become apparent in the following descrip-.

tion of the preferred method of operation. FIG. 9 illustrates the pipe bending system in place to bend pipe.

The internal support mandrel 112 is resting in its stored position in the outboard end of the stiffback 32. A length of pipe 73 is brought into the pipe bending machine 20 from the pin-up end thereof. The length of pipe 73 is generally handled by a tractor and crane assembly 167 or the like. The pipe 73 is moved into and longitudinally along within the pipe bending machine 20 to a position where its forward end is adjacent the mandrel 112. The mandrel 112 is then activated and moved into the pipe 173. The pipe is then moved further along within the pipe bending machine 20 to the preselected position for imparting the first 1 bend thereto. The mandrel 112, which of course moved with the pipe 73, is again activated and moved to its correct position with respect to the bending die 30 to support the pipe during the bend.- The mandrel 112 can be properly located in the pipe with a -reach rod" attached to controls on the mandrel or by the use of an automatic positioning apparatus such as is described in the copending application of Edward A. Clavin, Donald H. McCullough and David R. McCullough, Ser. No. 129,702, filed Mar. 31, 1971. FIG. 10 illustrates schematically the pipe 73 moved into the pipe bending machine in the position for the first bend and the collapsed mandrel 112 positioned within the pipe. It should be noted that the pipe preferably is moved completely through the pipe bending machine 'so that the first bend is applied to the rear end of the pipe.

As illustrated in FIG. 11, since the rearend of the pipe 73 is in close proximity to the bending die 30 and nearly aligned with the pin-up shoe 57 and pin-up clamp 66, the internal pin-up support 111 is inserted therein. The operator then causes the pin-up support 111 to expand and the stiffback clamp 72 to close. The operator also transmits signals to the mandrel 11-2 to cause it to operate. The signals to the mandrel preferably are transmitted by the reach rod or by electrical lines connecting the mandrel to the operators control station. There are two preferred methods of operating the improved internal support mandrel 112. The hydraulic packers may be pressurized first and the upper and lower assemblies then moved into contact with the pipe. Or the upper and lower assemblies may first be moved into contact with the pipe and the hydraulic packers then pressurized. Utilizing the former method with the hydraulic packers maintained at constant pressures throughout the various bends is often advantageous because it allows the mandrel to be expanded and contracted very rapidly. v

As illustrated in FIG. 12, the operator then causes the hydraulic fluid pressure to the outboard and inboard stiffback cylinder and piston assemblies to be increased 'such that the stiffback is raised sufficiently to bring the pipe 73 into contact with the bending die 30. Likewise,

the pin-up cylinder and piston assembly is pressurized whereby the wedges 64 move the pin-up shoe upwardly into firm contact with the rearward end of the pipe. The pin-up clamp 66 is then closed.

At this point in the bending process the previously described sequence valve in the hydraulic system of the inboard and outboard stiffback cylinder and piston assemblies is utilized. The hydraulic pressure in the inboard stiffback cylinder and piston assemblies is increased to a selected magnitude, such as, 1,200 psi, before any additional pressure is supplied to the outboard stiffback cylinder and piston assemblies. This insures that once the outboard stiffback cylinder and piston assemblies start moving the outboard stiffback shaft 52 upwardly, sufficient vertical forces will have already been applied to the two inboard stiffback shafts 35 that they will conjunctively function as a pivot for the stiffback 32.

FIG. 13 illustrates the improved pipe bending system according to this invention applying bend to the pipe. The stiffback '32 is. tilted upward about the pivot point formed by the inboard stiffback shafts 35. The pin-up I shoe 57 functions as the fulcrum or support for the rear end of the pipe. The pin-up shoe 57, the pin-up clamp 66 and the internal pin-up support 111 prevent the rear end of the pipe from becoming out-of-round. The stiffback clamp 72 and the stiffback 32 prevent the forward end of the pipe from becoming out-of-round. And the mandrel 112 prevents the pipe from buckling, wrinkling or crimping inwardly in the vicinity of the bend. The improved mandrel 112 according to this invention is positioned with respect to the bending die so thata portion of the upper assembly of the mandrel extends beyond the stifflaack or forward end of the die.,This is because the bending of the pipe occurs on a relatively small section of the bending die 30 near its forward end. Also, as illustrated in exaggerated form in FIG. 22, large diameter, thin-walled pipe 73 tends to buckle outwardly immediately adjacent the forward end of the die 30 and ripple or buckle 169 inwardly just beyond the 'outward bulge 168 as a result of the bending process.

Thus, as illustrated in FIG. 23, the mandrel 112 is positioned so that its upper assembly extends beyond the forward end of the bending die 30 sufficiently to support the pipe in the area of these bulges. Prior art internal pipe supporting mandrels, even if positioned properly with respect to the die, do not prevent these bulges. The improved mandrel 112 according to this invention prevents the inward bulges 169 and thus diminishes the outward bulge 168 and completely prevents the pipe from buckling, wrinkling or crinkling inwardly between the die and the stiffback in the region of the bend. The improved mandrel according to this invention 'accomplsihes this superior support of the pipe for several reasons. First, the use of the plurality of individual mechanical apparatus for moving the upper and lower assemblies apart and locking them apart insures that, while the mandrel is longitudinally flexible, the downward forces on the convex foundation support of the upper assembly are rigidly transferred to the lower assembly. Second, the use of a plurality of distinct elongated hydraulic packers on the upper assembly insures that downward forces applied to one segment of the mandrel are integrated through other segments of the mandrel. For example, assume that each of the five center packers are pressurized to 800 psi. As the pipe is bent upwardly against the die, the pressure of the interior of the pipe wall against the urethane envelope may increase the pressure of the apex packer at one point along its length to L200 psi. Other adjacent packers may be increased a lesser amount. These increased pressures are communicated throughout the length of the elongated interconnected packers and function to increase the support of the pipe. The integrating nature of the pressures in the packers causes the mandrel to support the pipe firmly along the entire length of the mandrel and thus prevent any inward bulging. All the while the mandrel remains longitudinally flexible. Third, the use of a plurality of distinct elongated hydraulic packers on the upper assembly hydraulically interconnected in sets facilitates better control of the shape of the pipe. Indeed, pipe which may be irregularly shaped prior to the bend will be circular after the bend.

FIG. 14 illustrates the pipe 73 after the first bend has been imparted thereto and it has been moved to the position for the next bend. After the first bend, the mandrel 112 is collapsed and the pin-up clamp 66 opened.

The pin-up shoe 57 and the stiffback 32 are then lowered. The stiffback clamp 72 is then released and the internal pin-up support 111 removed from the end of the pipe. A cable from winch 99 is hooked to the forward end of the pipe 73 and the pipe moved longitudinally toward the pin-up end of the machine for the next bend. The mandrel is then re-positioned. The entire bending process, excluding the use of the internal pinup support 111, described with respect to FIGS. 10 through 14 is then repeated as many times as necessary. When the forward end of the pipe approaches the stiffback clamp 72, internal stiffback support is utilized. The conjunctive use of the stiffback clamp 72 and the internal stiffback support 110 allow the pipe to be bent accurately and properly much closer to the forward end of the pipe than allowed by prior art systems. Likewise, the conjunctive use of the pin-up clamp and the internal pin-up support allow improved bending much closer to the rearward end of the pipe.

Thus, this invention provides an improved pipe bending system including an improved pipe bending machine and an improved internal pipe supporting mandrel. Many variations in the form of the preferred embodiment will now be apparent to those skilled in the art. For instance, the internal stiffback and pin-up support may depend from the mandrel. Additionally, many structural and hydraulic changes may be made in the various components of the system without departing from the invention. Therefore, the invention should not be limited to the preferred embodiment, but rather should extend to the full scope and spirit of the invention defined in the appended claims. 

1. An improved internal pipe supporting mandrel for use in a machine having a bending die and a stiffback, comprising: an elongated upper pipe-engaging assembly including at least one elongated inflatable bag mounted longitudinally along the upper assembly for providing internal support to the area of the pipe which is in contact with the bending die during the bending process; an elongated lower pipe-engaging assembly for engaging at least a part of the internal surface of the pipe in the area of the pipe which is in contact with the stiffback; and means for moving the upper and lower assemblies away from each other and thereby forcing the upper and lower assemblies into engagement with the pipe.
 2. An improved internal pipe supporting mandrel according to claim 1, including means for inflating the inflatable bag to a selected pressure.
 3. An improved internal pipe supporting mandrel according to claim 1, including means for moving the mandrel longitudinally along within the supporting surface, the moving means depending from the upper assembly so that they are in contact with the supporting surface when the upper and lower assemblies are contracted toward each other and are not in contact with each other when the assemblies are expanded away from each other.
 4. An improved internal pipe supporting mandrel according to claim 1, wherein the upper assembly includes an elongated, longitudinally flexible, transversely plano-convex foundation assembly supporting a resiliently compressible pipe-engaging material enveloping a plurality of elongated inflatable bags.
 5. An improved internal pipe supporting mandrel according to claim 4, wherein the plurality of inflatable bag are constructed to be filled with hydraulic fluid and are hydraulically interconnected in selected sets so that the pressures of the fluid supplied to the various sets of the bags can be varied.
 6. An improved internal pipe supporting mandrel according to claim 1, wherein the lower assembly includes an elongated, longitudinally flexible, transversely plano-convex foundation assembly supporting pipe engaging means.
 7. An improved internal pipe supporting mandrel according to claim 1, wherein the means for moving the upper and lower assemblies apart from each other and into engagement with the pipe include: opposing cam surfaces and shoulders mounted on the upper and lower assemblies at selected locations intermediate their lengths; at least one toggle bar mounted for horizontal movement between the opposing cam surfaces and shoulders at each location, each toggle bar including opposing surfaces for engaging the opposing cam surfaces and shoulders; and means for moving the toggle bars selectively horizontally whereby the upper and lower assemblies are moved away from each other by the toggle bars engaging the cam surfaces and thereby the shoulders and the toggle bars form a sturdy, continuous mechanical support between the upper and lower assemblies when the assemblies are in engagement with the pipe.
 8. An improved internal pipe supporting mandrel comprising: an upper assembly for providing support to the interior of the upper wall of the pipe along a preselected length thereof from the apex of the pipe to preselected transverse points either side thereof, the upper assembly including at least one inflatable bag for maintaining a constant pressure against the interior of a selected longitudinal segment of the upper wall of the pipe; a lower assembly for providing support to the interior of the lower wall of the pipe along the preselected length thereof from the nadir of the pipe to preselected transverse points either side thereof; and means secured to the upper assembly and to the lower assembly for selectively moving the assemblies away from and toward each other and into and out of contact with interior of the wall of the pipe.
 9. An improved internal pipe supporting mandrel according to claim 8, including means for moving the mandrel into, along and out of the pipe depending from the upper assembly whereby the means for moving the mandrel are in contact with the interior of the wall of the pipe when the upper and lower assemblies are contracted and are not in contact with the pipe when the upper and lower assemblies are expanded.
 10. An improved internal supporting mandrel according to claim 8, wherein the upper assembly includes: an elongated, longitudinally flexible, transversely plano-convex foundation assembly; a resiliently compressible pipe engaging material having a plurality of holes longitudinally therethrough attached to the convex surface of the foundation; an elongated hydraulically inflatable bag held in each of the holes in the resiliently compressible material, the bags being hydraulically interconnected in selected sets.
 11. An improved internal pipe supporting mandrel according to claim 8, including an internal expansible and contractible support assembly associated with and spaced from each end of the mandrel to provide support for the internal wall of the pipe at locations spaced from the mandrel.
 12. An improved internal pipe supporting mandrel according to claim 8, wherein the lower assembly includes: a plurality of substantially plano-convex support elements; a plurality of elongated steel string strips secured to each of the support elements around the outer convex surfaces thereof; and a plurality of resiliently compressible pipe engaging elements secured to the strips.
 13. An improved internal pipe supporting mandrel according to claim 8, wherein the means for selectively moving the upper and lower assemblies toward and away from each other includes: cam surfaces attached to each of the upper and lower assemblies; and means for selectively moving into contact with the cam surfaces and forcing apart the cam surfaces and the upper and lower assemblies attached thereto.
 14. An improved internal pipe supporting mandrel comprising: at least one elongated, planar rectangularly shaped, flexible support member; plano-convex end plates secured to each end of the elongated support member; a plurality of curved support elements secured to the elongated support member between the end plates with a relatively small space between each of the curved support elements for longitudinal flexibility; the elongated support member and the plurality of of curved support elements conjunctively forming a foundation assembly; a plurality of elongated back-up strips extending longitudinally along the convEx exterior of the plurality of curved support elements; a resiliently compressible material extending longitudinally along the convex exterior of the plurality of the curved support elements and the back-up strips, the resiliently compressible material having a plurality of holes longitudinally therethrough and presenting a transversely convex exterior along its length with a plurality of receiving slots cored out of its exterior surface; a plurality of hydraulically inflatable bags held in holes in the resiliently compressible material and extending through holes in the end plates; a plurality of elongated tie-bars secured to the end plates and extending through holes in the resiliently compressible material; and a plurality of elongated surface integrating strips secured to the end plates and extending throughout the length of the resiliently compressible material in the receiving slots therein.
 15. An improved internal pipe supporting mandrel according to claim 14, including: a plurality of upper jaw members attached to the underside of the elongated support member transversely intermediate its length and presenting downwardly facing cam surfaces and shoulders; at least one toggle bar pivotally linked to each jaw member; a plurality of lower jaw members, each of which is pivotally linked to a toggle bar, and which presents upwardly facing cam surfaces and shoulders and a downwardly facing convex surface; each toggle bar includes surfaces for engaging the cam surfaces and shoulders of the upper and lower jar members; a plurality of elongated strips secured to and extending longitudinally along the convex exterior of the lower jar member; a plurality of pipe engaging resiliently compressible elements attached to the elongated strips of the lower jar member; and at least one cylinder and piston assembly operatively connected to each toggle bar for moving the toggle bar. 